MONITORING DEVICE, AND METHOD OF ADJUSTING A FIXED MONITORING DEVICE
A fixed monitoring device is disclosed comprising an image collector arrangement and a first adjustment arrangement. The adjustment arrangement comprises a main gear arranged to rotate for adjusting a placement of the image collector arrangement, a first motor, a second motor, a first gearing arrangement operatively connecting said first motor to said main gear, a second gearing arrangement operatively connecting said second motor to said main gear. Each of the first and second gearing arrangements are self-locking. A method of adjusting a fixed monitoring device is also disclosed.
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This application claims the benefit of European Patent Application No 14175038.0 filed on Jun. 30, 2014, which is incorporated by reference as if fully set forth.
FIELD OF INVENTIONThe present invention relates to a fixed monitoring device comprising an image collector arrangement and an adjustment arrangement for adjusting a placement of the image collector arrangement. The invention also relates to a method of adjusting a fixed monitoring device.
BACKGROUNDIn fixed monitoring devices, such as fixed monitoring cameras and fixed Passive InfraRed (PIR) sensors, it is often necessary to adjust a placement of the image collection arrangement of the monitoring device. For many monitoring devices, this may be done manually during installation, by turning the monitoring device to a desired position, such that a desired field of view may be achieved. However, in some situations such manual adjustment is not satisfactory, because the installer cannot check the achieved field of view during manual adjustment. This may necessitate the involvement of two people, one of them adjusting the placement of the monitoring device, and the other checking the achieved field of view, e.g., watching a monitor to which images from the monitoring device are transmitted. In some instances, the fixed monitoring device may need to be adjusted after installation, and if the monitoring device is mounted in a place that is difficult to reach, manual adjustment may be impractical.
In an aim to solve these problems, fixed monitoring devices have been proposed whose placement may be adjusted remotely. For instance, there are fixed monitoring cameras in which the lens and image sensor assembly may be rotated by means of a main gear, to which a motor is connected via a gearing arrangement. The motor drives the main gear in rotation until a desired rotary position of the lens and image sensor assembly has been reached. In order to ensure that, once the desired rotary position has been reached, that position is maintained, a gearing arrangement providing a high frictional resistance is used. Thus, when the motor is stopped, the frictional forces in the gearing arrangement prevent further rotation of the main gear, thereby ensuring that the lens and image sensor assembly is kept in position. This may in many instances be a satisfactory solution, but the high frictional forces that have to be overcome place high requirements on the motor used. High requirements are also placed on the gears in terms of tolerances and play. Therefore, in some cases, it would be desirable to have an adjustment arrangement that may be manufactured at a lower cost, or that may require less space.
SUMMARYIt is an object of the invention to provide a fixed monitoring device having an adjustment arrangement that may be manufactured at a low cost. Another object is to provide a fixed monitoring device having an adjustment arrangement that may require little space. It is also an object to provide a method of adjusting a fixed monitoring device that may be implemented cost effectively, and that may ensure that the image collector arrangement of the monitoring device is maintained securely in position after adjustment, without requiring a large and expensive adjustment arrangement.
According to a first aspect, these and other objects are achieved, in full or at least in part, by a fixed monitoring device comprising an image collector arrangement and a first adjustment arrangement, said adjustment arrangement comprising: a main gear arranged to rotate for adjusting a placement of said image collector arrangement, a first motor, a second motor; a first gearing arrangement operatively connecting said first motor to said main gear, a second gearing arrangement operatively connecting said second motor to said main gear, said first and second gearing arrangements each being self-locking. By having two motors, it may be possible to use smaller, less expensive motors, since they can be used cooperatively to rotate the main gear. Additionally, by utilizing gearing arrangements which are self-locking, it may be ensured that the main gear is not rotated further after the motors have been stopped, without having to use gears providing high frictional resistance. This also makes it possible to use a smaller, less expensive motor, since the motor does not have to overcome a high frictional force for rotating the main gear. Using two smaller motors may make it easier to fit the motors in a housing of a monitoring device than if one larger motor is used.
As used herein, the terms “fixed monitoring device” and “fixed camera”, refer to monitoring devices and cameras, respectively, which are in themselves incapable of panning, tilting, and rolling.
Further, the term “adjustment” is to be understood as a movement undertaken primarily during installation of a fixed monitoring device, and hence not the movements performed by, e.g., a pan-tilt-zoom (PTZ) camera during operation. Adjustments may be made at the initial installation of a monitoring device, as well as at a point in time after the monitoring device has been installed.
According to an embodiment, at least one of said first and second gearing arrangements comprises a worm. A worm drive may ensure a secure locking of the adjustment arrangement when the motors are stopped. Further, it may be made compact, and may reduce the rotation speed from the motor to the main gear, and provide a high torque to the main gear in an efficient manner.
Adjusting a placement of said image collector arrangement may comprise adjusting a rotary position of said image collector arrangement. In this manner, the fixed monitoring device may be adjusted to cover a desired field of view.
Adjusting a placement of said image collector arrangement may comprise adjusting a distance between a sensor and an optical arrangement of said image collector arrangement. In this manner, the fixed monitoring device may be adjusted to obtain a desired focus.
In one embodiment, said first and second motors are arranged to co-operatively rotate said main gear in a first direction for rotating said image collector arrangement. Hereby, even small motors may be used for rotating the main gear.
In another embodiment, one of said first and second motors is arranged to be stopped while another of said first and second motors is arranged to drive the corresponding gearing arrangement in a second direction, which is opposite to said first direction, for compensating for backlash in said first and second gearing arrangements. In this manner, it may be ensured that the image collector arrangement of the fixed monitoring device is adjusted securely to a desired placement. Alternatively, said other motor may be arranged to continue driving its corresponding gearing arrangement in said first direction for compensating for said backlash.
It should in this context be noted that, references to directions are made in relation to rotation of the main gear. However, it is not the main gear that should be rotated for compensating for backlash. Rather, it is desirable to keep the main gear still once it has reached a desired position, but the motor in question should drive the corresponding gearing arrangement in the way it does for rotating the main gear in the direction in question.
In yet another embodiment, one of said first and second motors is arranged to drive the corresponding gearing arrangement in said first direction while another of said first and second motors is arranged to drive the corresponding gearing arrangement in a second direction, which is opposite to said first direction, for compensating for backlash in said first and second gearing arrangements. This is another way of ensuring that the image collector arrangement of the fixed monitoring device is adjusted securely to a desired placement.
In still another embodiment, one of said first and second motors is arranged to drive the corresponding gearing arrangement in a second direction, which is opposite to said first direction, at a first speed, while another of said first and second motors is arranged to drive its corresponding gearing arrangement in said second direction at a second speed, which is different from said first speed, for compensating for backlash in said first and second gearing arrangements. This is also a way of ensuring that the image collector arrangement of the fixed monitoring device is adjusted securely to a desired placement.
The fixed monitoring device may comprise a control unit arranged to control a locking force provided by said other motor for locking said main gear based on a current of said other motor. Hereby, it may, in a practical way, be ensured that the main gear is securely locked in the desired placement. For instance, if a DC motor is used, the current supplied to the DC motor may be used as a measure of a force currently applied by the DC motor. Once a desired locking force has been applied, the motor may be stopped and still lock the main gear. Too high locking forces, that would risk damaging the gearing arrangement, may be avoided.
According to an embodiment, the fixed monitoring device further comprises a second and a third adjustment arrangement, wherein the first adjustment arrangement is arranged to adjust the rotary position of the image collector arrangement in a roll direction, the second adjustment arrangement is arranged to adjust the rotary position of the image collector arrangement in a pan direction, and the third adjustment arrangement is arranged to adjust the rotary position of the image collector arrangement in a tilt direction. With such adjustment arrangements, it is possible to adjust the fixed monitoring camera in rotation about three axes, thereby making it possible to adjust the image collector arrangement in all rotational directions to achieve a desired field of view.
The fixed monitoring device may be a fixed camera, wherein said image collector arrangement comprises a lens and an image sensor.
According to a second aspect, these and other objects are achieved, in full or at least in part, by a method of adjusting a fixed monitoring device having an image collector arrangement and a first adjustment arrangement, said method comprising: rotating a main gear of said first adjustment arrangement, thereby adjusting a placement of said image collector arrangement, wherein said main gear is rotated in a first direction by a first motor operatively connected to said main gear via a first gearing arrangement, and a second motor operatively connected to said main gear via a second gearing arrangement, said first and second motors cooperating to rotate the main gear until the image collector arrangement has reached a predetermined placement, and when said image collector arrangement has reached said predetermined placement, driving at least one of said first and second gearing arrangements in a second direction, which is opposite to said first direction until backlash in said first and second gearing arrangements has been compensated for. By this method, it may be possible to adjust a fixed monitoring device, without the need for a strong, expensive motor. Since two motors are used cooperatively, smaller, less expensive motors may be used. Further, fitting two small motors in a housing of a fixed monitoring device may be easier than fitting one larger motor. Driving one or both of the gearing arrangements in the second direction once the image collector arrangement has reached the predetermined placement makes it possible to ensure that the image collector arrangement is maintained in the desired placement, even if there is backlash due to tolerances in the gearing arrangement.
The method may comprise, when said image collector arrangement has reached said predetermined placement, stopping one of said first and second motors, and driving another of said first and second motors to drive the corresponding gearing arrangement until said backlash has been compensated for. This is a practical way of ensuring that the image collector arrangement is maintained in the desired placement. Alternatively, said other motor may continue driving its corresponding gearing arrangement in said first direction until said backlash has been compensated for.
When said backlash has been compensated for, said other motor may be stopped. Thereby, there is no need for power to the motors once the main gear has been secured in the predetermined position.
In a variant, the method comprises, when said image collector arrangement has reached said predetermined placement, driving one of said first and second motors to drive the corresponding gearing arrangement in said first direction, and driving another of said first and second motors to drive the corresponding gearing arrangement in said second direction until said backlash has been compensated for. This is another way of ensuring that the image collector arrangement is maintained in the desired placement.
In another variant, the method comprises, when said image collector arrangement has reached said predetermined placement, driving one of said first and second motors to drive the corresponding gearing arrangement in said second direction at a first speed, and driving another of said first and second motors to drive the corresponding gearing arrangement in said second direction at a second speed, which is different from said first speed, until said backlash has been compensated for. This is also a way of ensuring that the image collector arrangement is maintained in the desired placement.
When said backlash has been compensated for, the first and second motors may be stopped. In this manner, power consumption may be reduced.
Adjusting a placement of said image collector arrangement may comprise adjusting a rotary position of said image collector arrangement. In this manner the fixed monitoring device may be adjusted to cover a desired field of view.
Adjusting a placement of said image collector arrangement may comprise adjusting a distance between a sensor and an optical arrangement of said image collector arrangement. In this manner, the fixed monitoring device may be adjusted to obtain a desired focus.
In a variant of the method, a locking force provided by said other motor for locking said main gear is controlled based on a current of said other motor. Hereby, it is possible to ensure that the image collector arrangement is securely locked in the desired placement. It is also possible to avoid a too high locking force that would risk damaging the gearing arrangements.
A further scope of applicability of the present invention will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.
Hence, it is to be understood that this invention is not limited to the particular component parts of the device described or steps of the methods described as such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, a reference to “an object” or “the object” may include several objects, and the like. Furthermore, the word “comprising” does not exclude other elements or steps.
The invention will now be described in more detail by way of example and with reference to the accompanying schematic drawings, in which:
In
The adjustment arrangement 6 further comprises a control unit 16, which is arranged to monitor a power supply to the second motor 9 and control the second motor 9 based on the power supply. The power supply to a DC motor may be used as a measure of the force applied by the motor. Hence, by monitoring the power supply, or current, to the motor it is possible to determine when a desired locking force has been applied. Further, it is possible to avoid applying a locking force that is too high and would risk jamming and damaging the gearing arrangement.
At some point after the camera 1 has been mounted, e.g., in a ceiling or on a wall, it may be desirable to adjust a placement of the image collector arrangement 4, such that the camera 1 obtains a desired field of view for capturing a scene to be monitored. This may be immediately after mounting, or later, for instance if the environment around the camera 1 has changed, such that the image collector arrangement 4 needs to be adjusted to obtain a new desired field of view for capturing the scene. With a camera 1 in accordance with the embodiment shown in
A first adjustment arrangement 106 of the assembly has a first main gear 107, a first motor 108, a second motor 109, a first gearing arrangement 110 operatively connecting the first motor 108 to the first main gear 107, and a second gearing arrangement 111 operatively connecting the second motor 109 to the main gear 107. The first gearing arrangement 110 is here made up of a first worm drive, having a first worm 112 and a first worm gear 113. Similarly, the second gearing arrangement 111 is made up of a second worm drive, having a second worm 114 and a second worm gear 115. The first and second worm gears 113, 115 are self-locking, such that they may each be driven by the respective worm 112, 114, but cannot in turn drive the worm 112, 114.
A second adjustment arrangement 126 of the assembly has a second main gear 127, a third motor 128, a fourth motor 129, a third gearing arrangement 130 operatively connecting the third motor 128 to the second main gear 127, and a fourth gearing arrangement 131 operatively connecting the fourth motor 129 to the second main gear 127. The third gearing arrangement 130 is made up of a third worm drive, having a third worm 132, and a third worm gear 133, and the fourth gearing arrangement 131 is made up of a fourth worm drive, having a fourth worm 134, and a fourth worm gear 135. In the same way as for the first adjustment arrangement 106, the third and fourth worm gears 133, 135 are self-locking, such that they may each be driven by the respective worm 132, 134, but cannot drive the worm 132, 134.
Similarly, a third adjustment arrangement 146 of the assembly has a third main gear 147, a fifth motor 148, a sixth motor 149, a fifth gearing arrangement 150 operatively connecting the fifth motor 148 to the third main gear 147, and a sixth gearing arrangement 151 operatively connecting the sixth motor 149 to the third main gear 147. The fifth gearing arrangement 150 is, slightly different from the previously mentioned gearing arrangements, made up of a fifth worm drive, having a fifth worm 152. Similarly, the sixth gearing arrangement 151 is made up of a sixth worm drive, having a sixth worm 154. The fifth and sixth worms 152, 154 are self-locking, just like the first to fourth worm gears.
The first, second and third adjustment arrangements 106, 126, 146 are each rotatable about a first axis AP, a second axis AT, and a third axis AR, respectively. The three adjustment arrangements 106, 126, 146 make it possible to adjust the position of the image collector arrangement 104 in three rotational directions indicated by the arrows P1, P2, T1, T2, R1, and R2. By means of the first adjustment arrangement 106, the rotary position of the image collector arrangement 104 may be adjusted in a roll direction R1, R2. By means of the second adjustment arrangement 126, the rotary position of the image collector arrangement 104 may be adjusted in a pan direction P1, P2. It may be noted that, if the image collector arrangement is directed straight downwards, similar to the camera shown in
The method used for adjusting the rotary position of the image collector arrangement 104 of the camera according to the embodiment shown in
In the embodiments shown in
The adjustment arrangement 206 in
With reference to
The image sensor 330 is arranged on a printed circuit board or PCB 326, which in turn is arranged in a PCB holder 327. The PCB holder 327 is attached to a rack 328. The main gear 307 is operatively connected to the rack 328. Thus, by rotating the main gear 307, the PCB 326 with the image sensor 330 may be moved closer to or further away from the lens 305 for adjusting back focus of the camera 301.
The method of adjusting the position of the image sensor 330 in relation to the lens 305 may be essentially the same as the method described above in connection with
It will be appreciated that a person skilled in the art can modify the above described embodiments in many ways and still use the advantages of the invention as shown in the embodiments above. As an example, other self-locking gearing arrangements may be used, such as Geneva drives, or internal Geneva drives. Further, a gearing arrangement with a train of gears providing a large total gear ratio (e.g., 100:1) may also provide the desired self-locking function. As compared to a worm drive, a large gear ratio gear train may make it possible to achieve a higher efficiency. This is because if a worm drive is formed with a sufficiently small angle to provide a self-locking effect, the efficiency is reduced. Still, worm drives may generally require little space, and may be made at a low cost. It is also possible to employ a combination of a worm drive and a large gear ratio gear train, with part of the self-locking function performed by the worm drive, and part of it performed by the large gear ratio gear train.
Regardless of what part of the gearing arrangement provides the self-locking function, this part may be placed anywhere between the motor and the main gear. For instance, in a gearing arrangement with a worm and two gears between the motor and the main gear, the worm may be arranged directly engaging the motor, directly engaging the main gear, or somewhere between the other gears. It may here be noted that it may be practical to place the self-locking part of the gearing arrangement as close to the main gear as possible, since this reduces the number of gears that have to be in tension during locking. Thereby, the strain on the gears is reduced, allowing less expensive gears to be used, for instance gears made of plastic.
In the embodiments described above, the motors used are DC motors. An advantage of this kind of motor is that the force applied by them may easily be controlled by monitoring the current supplied to them. However, other motors may be used, for instance stepping motors. If a stepping motor is used, the locking force applied may be controlled by monitoring the number of steps performed by the stepping motor. In order to avoid applying a locking force that is too high and would risk jamming or damaging the gearing arrangement, the voltage supplied to the motor may be lowered during backlash compensation.
In the embodiments shown in
Even though it is only in the embodiment shown in
It should be noted that the numbering of the motors above as a first and a second motor is purely for simplification of the description. It does not matter which of the motors is stopped, and which is operated to rotate in the other direction. Still, if a control unit is used for controlling the locking force applied on the main gear after the main gear has been rotated to the desired position, that control unit should control the motor that is used for counter-rotation for overcoming backlash. If both motors are used for compensating for backlash, one or both motors may be monitored by one control unit monitoring the current to the one motor, one control unit monitoring both motors, or one control unit per motor.
Similarly, in the embodiment shown in
As described above, the backlash may be overcome by stopping one of the motors when the main gear has been rotated in one direction to the desired position, and then operating the other motor to rotate the main gear in the opposite direction until the backlash has been overcome. However, a similar result may be achieved by instead operating the motors to rotate the main gear in different directions, or by operating the motors to rotate the main gear in the same direction, but at different speeds. In the former case, once the main gear has been rotated in one direction to a desired position, one of the motors is operated to continue rotating the main gear in that direction, whereas the other motor is operated to rotate the main gear in the opposite direction until the backlash has been overcome. In the latter case, once the main gear has been rotated in one direction to a desired position, both motors are operated to rotate the main gear in the opposite direction, but at different speeds, until the backlash has been overcome.
Instead of arranging the control unit to monitor the power supply to the second motor, the control unit may be arranged to monitor the power supply to the first motor. Further, the control unit may be arranged to monitor the power supply to both motors. Alternatively, two control units may be employed, each monitoring a respective one of the motors.
In the embodiment described in connection with
In
The motors of the adjustment arrangement may be powered using a power cord also powering the general camera functions, or using a separate power cord. Alternatively, the motors may be powered via an Ethernet cable, using Power over Ethernet, PoE.
The cameras for which the adjustment arrangements and methods described above are useful may be any type of cameras, such as fixed cameras or fixed dome cameras. Further, the cameras may have any type of sensor, e.g., sensors capturing visible light or infrared light, or micro bolometers.
It should also be noted that the invention is not limited to cameras or monitoring cameras. It is useful also for other types of monitoring devices, such as PIR sensors and microphones.
Thus, the invention should not be limited to the shown embodiments but should only be defined by the appended claims.
Claims
1. A fixed monitoring device comprising an image collector arrangement and a first adjustment arrangement, said adjustment arrangement comprising:
- a main gear arranged to rotate for adjusting a placement of said image collector arrangement,
- a first motor,
- a second motor;
- a first gearing arrangement operatively connecting said first motor to said main gear,
- a second gearing arrangement operatively connecting said second motor to said main gear,
- said first and second gearing arrangements each being self-locking.
2. The fixed monitoring device as claimed in claim 1, wherein at least one of said first and second gearing arrangements comprises a worm.
3. The fixed monitoring device as claimed in claim 1, wherein adjusting a placement of said image collector arrangement comprises adjusting a rotary position of said image collector arrangement.
4. The fixed monitoring device as claimed in claim 1, wherein adjusting a placement of said image collector arrangement comprises adjusting a distance between a sensor and an optical arrangement of said image collector arrangement.
5. The fixed monitoring device as claimed in claim 1, wherein said first and second motors are arranged to cooperatively rotate said main gear in a first direction for rotating said image collector arrangement.
6. The fixed monitoring device as claimed in claim 5, wherein, for the purpose of compensating for backlash in said first and second gearing arrangements:
- one of said first and second motors is arranged to be stopped while another of said first and second motors is arranged to drive the corresponding gearing arrangement in a second direction, which is opposite to said first direction, or
- one of said first and second motors is arranged to be stopped while another of said first and second motors is arranged to drive the corresponding gearing arrangement in the first direction, or
- the first and the second motor are arranged to drive the respective gearing arrangements in opposite directions, or
- the first and the second motor are arranged to drive the respective gearing arrangements in the same direction but at different speeds.
7. The fixed monitoring device as claimed in claim 6, further comprising a control unit arranged to control a locking force provided by said other motor for locking said main gear based on a current of said other motor.
8. The fixed monitoring device as claimed in claim 1, further comprising a second and a third adjustment arrangement, wherein
- the first adjustment arrangement is arranged to adjust the rotary position of the image collector arrangement in a roll direction,
- the second adjustment arrangement is arranged to adjust the rotary position of the image collector arrangement in a pan direction, and
- the third adjustment arrangement is arranged to adjust the rotary position of the image collector arrangement in a tilt direction.
9. The fixed monitoring device as claimed in claim 1, said fixed monitoring device being a fixed camera, wherein said image collector arrangement comprises a lens and an image sensor.
10. A method of adjusting a fixed monitoring device having an image collector arrangement and a first adjustment arrangement, said method comprising
- rotating a main gear of said first adjustment arrangement, thereby adjusting a placement of said image collector arrangement,
- wherein said main gear is rotated in a first direction by a first motor operatively connected to said main gear via a first gearing arrangement, and a second motor operatively connected to said main gear via a second gearing arrangement,
- said first and second motors cooperating to rotate the main gear until the image collector arrangement has reached a predetermined placement, and
- when said image collector arrangement has reached said predetermined placement,
- driving at least one of said first and second gearing arrangements in a second direction, which is opposite to said first direction until backlash in said first and second gearing arrangements has been compensated for, or
- driving at least one of said first and second motors in the first direction until backlash in said first and second gearing arrangements has been compensated for, or
- driving said first and second motors in opposite directions until backlash in said first and second gearing arrangements has been compensated for.
11. The method as claimed in claim 10, comprising, when said image collector arrangement has reached said predetermined placement,
- stopping one of said first and second motors, and
- driving another of said first and second motors to drive the corresponding gearing arrangement in said second direction until said backlash has been compensated for.
12. The method as claimed in claim 10, wherein when said backlash has been compensated for, said other motor is stopped.
13. The method as claimed in claim 10, wherein adjusting a placement of said image collector arrangement comprises adjusting a rotary position of said image collector arrangement.
14. The method as claimed in claim 10, wherein adjusting a placement of said image collector arrangement comprises adjusting a distance between a sensor and an optical arrangement of said image collector arrangement.
15. The method as claimed in claim 10, wherein a locking force provided by said other motor for locking said main gear is controlled based on a current of said other motor.
Type: Application
Filed: Jun 29, 2015
Publication Date: Dec 31, 2015
Applicant: AXIS AB (Lund)
Inventor: Fredrik Sterngren (Lund)
Application Number: 14/753,049